Cross-Coupling of Triallyl(aryl)silanes with Aryl Bromides and Chlorides: An Alternative Convenient Biaryl Synthesis

Synthesis of C3'-Foused Aryl/Penta-1,4-Dien-3-One/Amine Hybrids as HSP90C-Terminal Inhibitors

24 C3'-focused hybrids of aryl/penta-1,4-dien-3-one/amine (APDA) were designed and synthesized. Of these hybrids, 2 n demonstrated improved antiproliferative effects on HER2-positive breast cancer cells (SKBr3 and BT474) and triple-negative breast cancer (TNBC) cells (MDA-MB-231 and MDA-MB-468) with IC50 values ranging from 7.45 to 10.75 μM, but less toxicity to normal breast cells MCF-10A than the first generation of hybrid 1. Additionally, 2 n retained its ability to inhibit HSP90C-terminus, leading to the degradation of HSP90 client proteins HER2, EGFR, pAKT, AKT, and CDK4, without inducing a heat-shock response. Notably, 2 n also demonstrated improved thermostability compared to 1 and maintained in vitro metabolic stability in simulated intestinal fluid. These findings will provide a scientific basis for developing HSP90C-terminal inhibitors in the future.

Palladium-catalyzed Hiyama cross-couplings of pyrimidin-2-yl tosylates with organosilanes

An efficient palladium-catalyzed Hiyama reaction between various pyrimidin-2-yl tosylates with organosilanes has been developed. The use of CuCl with TBAF as additive is essential for promotion of the construction of the carbon–carbon bond. This procedure shows wide functional group tolerance for electrophilic pyrimidin-2-yl tosylates and has been extended to aromatic amino-substituted pyrimidin-2-yl tosylates, affording the desired C2-aryl and alkenyl pyrimidine derivatives in good to excellent yields.

Suzuki–Miyaura Coupling Reactions of Fluorohalobenzenes

Organofluorine compounds have gained interest in the fields of pharmaceuticals, agrochemicals, diagnostics, materials, and catalysis. Suzuki–Miyaura coupling reactions of fluorinated arenes made a tremendous impact in chemical and biological research and made organofluorinated molecules more readily available. This review gives a brief summary of Suzuki–Miyaura coupling reactions of fluorinated benzene derivatives. In this context, various aspects, such as regio­selectivity, efficiency, and applications, are discussed.

1 Introduction

2 Organofluorine Compounds

3 Suzuki–Miyaura Reactions of Fluorohalobenzenes

3.1 Fluorophthalates

3.2 Reactions of Pentafluorohalobenzenes

3.3 Tetrafluorohalobenzenes

3.4 Trifluorohalobenzenes

3.5 Difluorohalobenzenes

3.6 Monofluorohalobenzenes

3.7 Halo(trifluoromethyl)benzenes

3.8 Trifluoromethyl Pyridines

4 S Summary

Palladium-catalyzed cross-coupling of (hetero)aryl or alkenyl sulfonates with aryl titanium as the multi-functional reagent

The first palladium-catalyzed cross-coupling reaction of aryl/heteroaryl and alkenyl mesylates and tosylates with aryl titanium as the multi-functional reagent is reported.

Electrochemical Arylation Reaction

Arylated products are found in various fields of chemistry and represent essential entities for many applications. Therefore, the formation of this structural feature represents a central issue of contemporary organic synthesis. By the action of electricity the necessity of leaving groups, metal catalysts, stoichiometric oxidizers, or reducing agents can be omitted in part or even completely. The replacement of conventional reagents by sustainable electricity not only will be environmentally benign but also allows significant short cuts in electrochemical synthesis. In addition, this methodology can be considered as inherently safe. The current survey is organized in cathodic and anodic conversions as well as by the number of leaving groups being involved. In some electroconversions the reagents used are regenerated at the electrode, whereas in other electrotransformations free radical sequences are exploited to afford a highly sustainable process. The electrochemical formation of the aryl-substrate bond is discussed for aromatic substrates, heterocycles, other multiple bond systems, and even at saturated carbon substrates. This survey covers most of the seminal work and the advances of the past two decades in this area.

Mild base-promoted benzannulation for the construction of polyfunctionalized m-terphenyl derivatives and their application as potent UV-filters

An efficient and facile transition-metal-free benzannulation was developed for the construction of polyfunctionalized m-terphenyl derivatives.

Palladium-Catalyzed Desilylative Acyloxylation of Silicon-Carbon Bonds on (Trimethylsilyl)arenes: Synthesis of Phenol Derivatives from Trimethylsilylarenes

A strategy for desilylative acetoxylation of (trimethylsilyl)arenes has been developed in which (trimethylsilyl)arenes are converted into acetoxyarenes. The direct acetoxylation is performed in the presence of 5 mol % of Pd(OAc)2 and PhI(OCOCF3)2 (1.5 equiv) in AcOH at 80 °C for 17 h. The acetoxyarenes are obtained in good to high yields (67-98%). The synthetic utility is demonstrated with a one-pot transformation of (trimethylsilyl)arenes to phenols by successive acetoxylation and hydrolysis. Furthermore, desilylative acyloxylation of 2-(trimethylsilyl)naphthalene using several carboxylic acids has been conducted.

Synthesis, Characterization, and Nanocatalysis Application of Core–Shell Superparamagnetic Nanoparticles of Fe3O4@Pd

There is a wide number of different synthetic methods to obtain magnetite (Fe3O4) superparamagnetic nanoparticles (SPNPs). However, only a few are able to produce very small and well defined SPNPs with narrow size distribution. We report a modification of the metal-complex decomposition in organic media method in which we replace iron(iii) acetylacetonate (Fe(Acac)3) with an iron–urea complex (Fe-Urea) as metal source for the synthesis. With this modification we were able to obtain small particle sizes with a good control in size distribution. The Fe-Urea complex is easy to prepare with excellent yields. Core–shell nanoparticles are then prepared using palladium(ii) acetylacetonate as a Pd source, to obtain a Pd0 shell stabilised by oleylamine. The core–shell superparamagnetic nanoparticles of Fe3O4@Pd-OA are extensively characterized by FT-IR, powder X-ray diffraction, transmission electron microscopy, UV-vis, thermogravimetric analysis/differential scanning calorimetry, and magnetic susceptibility measurements, and tested in a palladium-catalyzed cross-coupling Suzuki–Miyaura reaction with promising results.

[Efficient synthesis of multisubstituted aromatic compounds from phenol derivatives]

Phenols are abundant in nature and diverse phenols are readily available commercially at low cost. Thus, phenols can be used as the raw materials for the synthesis of valuable multisubstituted aromatic compounds by the direct activation of phenolic hydroxyl groups (C-O bond activation), followed by substitutions with other substituents. Although the derivatization of phenolic hydroxyl groups to sulfonates, such as triflates, nonaflates, tosylates and mesylates, followed by the transition-metal-catalyzed coupling reactions has been extensively investigated for this purpose, the direct C-O bond activation of phenols for subsequent functional group transformation has been a long-standing challenge in modern organic synthesis. In this review, I have summarized my recent studies on the formal direct C-O bond activation of phenols using nonafluorobutanesulfonyl fluoride (NfF) for the synthesis of multisubstituted aromatics. I have focused on the dual use of NfF, a less expensive commercially available reagent, including the tentative formation of highly reactive nonaflates from phenols and the use of the liberated fluoride ion as a nucleophile to promote the reactions of nonaflates. The following four topics are discussed: 1) palladium-catalyzed coupling reactions of phenols, 2) novel preparation of benzynes from 2-silylphenols, 3) synthesis of fluorinated aromatic compounds via the formation of benzynes, and 4) Hiyama coupling of (tert-butyldimethylsilyl)arenes activated by internal phenolic hydroxyl groups.

Palladium-catalysed cross-coupling of organosilicon reagents

The palladium catalysed cross-coupling of organosilicon reagents with organo halides and pseudo-halides has developed over the past 30 years into an efficient and attractive carbon-carbon bond forming strategy. Extensive research within this field to expand and diversify on the scope of the organosilicon coupling reaction will continue to promote its use in the synthesis of biologically and pharmaceutically important organic molecules. The recent advances made within this area are explored in this critical review (199 references).

Fluoride-promoted cross-coupling of chloro(mono-, di-, or triphenyl)germanes with aryl halides in "moist" toluene. Multiple transfer of the phenyl group from organogermane substrates and comparison of the coupling efficiencies of chloro(phenyl)germanes with their corresponding stannane and silane counterparts

The trichlorophenyl-, dichlorodiphenyl-, and chlorotriphenylgermanes undergo Pd-catalyzed cross-couplings with aryl bromides and iodides in the presence of tetrabutylammonium fluoride in toluene with addition of the measured amount of water. One chloride ligand on the Ge center allows efficient activation by fluoride to promote transfer of one, two, or three phenyl groups from the organogermanes. The corresponding chlorophenylstannanes were found to be more reactive than chlorophenylsilanes, which in turn were more effective than chlorophenylgermanes. One chloride ligand on the Ge or Si center allows efficient activation by fluoride to promote transfer of up to three aryl groups from germane or silicon. However, no haloligand was necessary to be present on the Sn center, since tetraphenyltin efficiently transferred up to four phenyl groups during fluoride-promoted couplings with aryl halides. (19)F NMR studies suggested formation of the fluorophenylgermanes and the hypervalent germanate species as possible intermediates.

Cross-coupling reactions of aromatic and heteroaromatic silanolates with aromatic and heteroaromatic halides

The alkali-metal salts (potassium and sodium) of a large number of aryl- and heteroarylsilanols undergo efficient cross-coupling with a wide range of aromatic bromides and chlorides under mild conditions to form polysubstituted biaryls. The critical feature for the success of these coupling reactions and their considerable scope is the use of bis(tri-tert-butylphosphine)palladium. Under the optimized conditions, electron-rich, electron-poor, and sterically hindered arylsilanolates afford cross-coupling products in good yields. Many functional groups are compatible with the coupling conditions such as esters, ketones, acetals, ethers, silyl ethers, and dimethylamino groups. Two particularly challenging substrates, (2-benzofuranyl)dimethylsilanolate and (2,6-dichlorophenyl)dimethylsilanolate prepared as their sodium salts showed excellent activity in the coupling reactions, in the former case also with aromatic chlorides. General methods for the efficient synthesis of a wide range of aromatic silanols are also described.

Silicon-based cross-coupling reactions in the total synthesis of natural products

Unlike other variants of transition-metal-catalyzed cross-coupling reactions, those based on organosilicon donors have not been used extensively in natural product synthesis. However, recent advances such as: 1) the development of mild reaction conditions, 2) the expansion of substrate scope, 3) the development of methods to stereoselectively and efficiently introduce the silicon-containing moiety, 4) the development of a large number of sequential processes, and 5) the advent of bifunctional bis(silyl) linchpin reagents, signify the coming of age of silicon-based cross-coupling reactions. The following case studies illustrate how silicon-based cross-coupling reactions play a strategic role in constructing carbon-carbon bonds in selected target molecules.